1. Field of the Invention
The present invention relates generally to an elastic wave device and a manufacturing method of the device, and, more particularly, to a surface acoustic wave device that can function as a filtering device or a resonator used in a functioning unit of, for example, a television set (hereinafter, “TV”), a video tape recorder (hereinafter, “VTR”), a DVD (Digital Versatile Disk) recorder, a portable phone, etc., or an elastic wave device such as an FBAR (Film Bulk Acoustic Resonator) using a piezoelectric film, and a manufacturing method of the devices.
2. Description of the Related Art
Currently, as an elastic wave device, a surface acoustic wave device (hereinafter, “SAW device”) is a variously used circuit that processes a wireless signal in a frequency band of, for example, a 45 MHz to 2 GHz band and is widely used in a transmission band-pass filter, reception band-pass filter, a local transmission filter, an antenna duplexer, an intermediate frequency filter, an FM modulator, etc.
An elastic wave device such as an FBAR has also been used as a filter in a frequency band of 1 GHz to 10 GHz.
Recently, downsizing of these signal processing devices has been progressed and a demand for downsizing of electronic parts such as a SAW device and an FBAR used therein is also getting stronger. Demand for multi-band portable phones that can be used in a plurality of different frequency bands is getting stronger and, for portable phones, downsizing and integration of devices are more strongly demanded than single-band devices.
In such a portable phone, a multi-filter incorporating a plurality of filters is used. For the filter, an example of a conventional configuration of a dual filter incorporating two filters is shown in FIGS. 1A, 1B, and 1C (Part I, Part II, and Part III).
FIG. 1A depicts a plan view of the configuration seen from the side of electrode terminal portions of a dual filter incorporating two filter chips C1 and C2. FIGS. 1B and 1C depict respectively a first example and a second example of a different dual filter having the plan configuration seen from the side of the electrode terminal of FIG. 1A common thereto, and depict cross-sectional views taken along a line A-B of FIG. 1A.
Similarly to a single filter, terminal electrodes include signal electrodes (an input terminal IN and an output terminal OUT) and ground electrodes GND and the number of the signal electrodes is increased corresponding to the number of chips. The ground electrodes GND are often made common to enhance the ground.
The cross-sectional view has a configuration as shown in FIG. 1B or FIG. 1C depending on the shape of a ceramic substrate that is an interposer.
In FIG. 1B, a ceramic substrate 1 has a container-like shape and, in the ceramic substrate 1, the filter chips C1 and C2 each formed with bumps thereon are fixed by flip chips 3. The container is closed with an airtight sealing layer 2 as a lid thereof. The space defined by bumps 3 between the filter chips C1 and C2 and the ceramic substrate 1 is propagating space 10 for comb-shaped electrodes formed respectively on the filter chips C1 and C2 that form SAW devices.
Inside the ceramic substrate 1, a re-wiring layer 11 is formed to move the wiring connected by the bumps 3 such that the wiring is placed at the positions and in the shapes of the terminal electrodes IN and OUT-C1 and OUT-C2. The re-wiring layer 11 is used when the ground wiring of the chips is shared.
FIG. 1C depicts the case where the ceramic substrate 1 is plate-shaped 1a and, similarly to the container-shaped type of FIG. 1B, the filter chips C1 and C2 each formed with the bumps 3 thereon are fixed by the flip chips 3. The airtight sealing layer 2 is formed such that the layer 2 covers over the filter chips C1 and C2. In the case of a plate-shaped ceramic substrate 1a, the entire size can be more downsized than the case of the container type by the space reduced due to absence of the frame. However, because the plate-shaped type also needs the propagating space 10 that is defined by the bumps 3, and the re-wiring layer 11 similarly to the case of the container-type, the thickness in the vertical direction is not varied compared to the case of the container-shaped substrate 1 of FIG. 1B.
In the case of a single filter, at the wafer level, downsizing and a thinner shape are being enabled by the packaging executed by forming the above propagating space 10 and the above re-wiring layer 11. An example of wafer-level packaging for a single filter has been proposed in a recent patent application by the inventors of the present application (Japanese Patent Application No. 2005-290969).
For a dual filter, because the optimal electrode film thickness, etc., differ for each frequency, each of a plurality of devices needs to be used separately as one chip and the same method as that used for the wafer-level packaging for a single filter can not be used.
However, techniques described in Japanese Patent Application Laid-Open Publication Nos. 1998-215143 and 1999-16845 are known as approaches for downsizing a plurality of chips at the chip-level. That is, as shown in these patent documents, a method of directly bonding the side faces of chips between the chips with each other is present and chips each formed in an electrode thickness suitable for each frequency for use are directly bonded with each other.
According to the invention described in the above '143 publication, as shown in FIGS. 2A and 2B quoted from the drawings depicted in the above '143 publication, two chips are integrated by bonding only the side faces of the chips with each other (15 in FIG. 2A) or only the upper portions and the lower portions of the side faces respectively with each other (16 and 17 in FIG. 2B).
Otherwise, according to the invention described in the above '845 publication, as shown in FIG. 3 quoted from the drawings depicted in the above '845 publication, only side faces of chips are bonded with each other to integrate the chips with resin adhesive Y having lower elasticity than that of a substrate X.
According to any one of the methods in the above patent documents, it is assumed that the chips are further accommodated in a container after their integration. Therefore, robustness is insufficient when the chips are used as an independent item after their integration.
The re-wiring layer 11 (FIGS. 1B and 1C) to connect a plurality of devices to each other is necessary for a multi-filter. However, in the method of the above '969 application, a wiring layer is formed in a container similarly to that of the conventional techniques of the above '143 and '845 publications and, therefore, the device can not be made thinner in the thickness direction.